rtw88: 8723d: Add RF read/write ops

8723D use SIPI to indirectly read RF register instead of directly read,
so introduce a new struct rtw_rf_sipi_addr and new function
rtw_phy_read_rf_sipi(). Since other chips don't use the new function,
only 8723D needs to fill struct rtw_rf_sipi_addr in rtw_chip_info.

Because there are two kinds of functions for reading RF registers now,
change rtw_phy_read_rf() to chip->ops->read_rf() in
rtw_phy_write_rf_reg_sipi() so that we can switch tp proper RF read
functions depends on the type of the chip.

Though 8723D is an 1x1 chip, it has two RF PHY and we can switch to
one of them, and that should be configured properly. Hence, add a
fix_rf_phy_num to struct rtw_chip_info to allow driver to set one of
the PHY's registers for 8723D, even it is only 1x1. Another variable
rf_phy_num is introduced to keep the constraint number of RF path we
can access, and its value is:
	rf_phy_num = (fix_rf_phy_num ? fix_rf_phy_num : rf_path_num)

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200420055054.14592-5-yhchuang@realtek.com